Peer victimization (PV; i.e., bully victimization, sexual harassment) is pervasive and has been associated with adverse outcomes including emotional distress and substance use among adolescents. Although there is clearly the potential for PV to cause harm, not all adolescents suffer serious effects from such experiences. Little is known about the conditions under which PV causes harm and for whom. There is a surprising lack of research to illuminate: (a) the individual, social and situational factors that influence an individual's response to victimization proximally and over time; and (b) the role of PV in the development of substance use. The proposed study will investigate the acute and long-term effects of PV on adolescent well-being and substance use. Two complimentary methods of data collection to be used: a longitudinal web-based survey comprised of multiple short-interval assessment over a two-year period and a daily diary study of PV experienced over an eight-week period. Adolescents ages 13 - 15 years, will be recruited via address based sampling to participate. The proposed research will advance current understandings of the conditions under which PV is deleterious and for whom, and will identify the processes through which PV affects the development of substance use. It is guided by the following Specific Aims: 1. what are the acute, proximal effects of PV on emotional distress (e.g., negative effect, anxiety) and on substance use among adolescents? 2. Are there individual or situational variables that moderate the association between PV and proximal outcomes? Do the effects of PV vary across three dimensions: victim characteristics (e.g., gender), the characteristics of the PV experience (e.g., chronicity), and potential buffers (e.g., parent, and peer support)? 3. What are the long-term effects of PV on emotional distress and substance use? The effects of PV on trajectories of emotional distress and substance use over time will be examined, as will potential mediators (e.g., depression) and moderators (e.g., alcohol coping expectancies) of PV to identify who is most at risk of developing a substance use problem following PV. The use of multiple methods to address these aims is highly novel and offers the potential to significantly advance understandings of PV.